Ball point pen back end closure

ABSTRACT

A pen plug particularly useful in ballpoint pens as a stopper to prevent back leakage of ink from the ink reservoir of such pens and yet function to allow passage of air into the pen interior. Such plugs include a plurality of substantially continuous synthetic filaments such as cellulose acetate, natural fibrous threads and synthetic filaments or mixtures of differing synthetic filaments encased in a plastic sheath.

United States Patent 1191 Dick 1 1451 July 9, 1974 BALL POINT PEN BACKEND CLOSURE [75] Inventor: Franklin Dick, New York, NY.

[73] Assignee: Dart Industries Inc., Los Angeles,

Calif.

22 Filed: Aug. 3, 1970 21 Appl. No.: 60,318

3,464,775 9/1969 Beal 401/199 FOREIGN PATENTS OR APPLICATIONS 1,164,7459/1969 Great Britain 401/217 1,229,524 3/1960 France 401/217 806,3316/1951 Germany 401/217 Primary ExaminerLawrence Charles Attorney, Agent,or Firm-Leigh B. Taylor; Kenneth J. I-Iovet; Paul R. Wylie ABSTRACT Apen plug particularly useful in ballpoint pens as a stopper to preventback leakage of ink from the ink reservoir of such pens and yet functionto allow passage of air into the pen interior. Such plugs include aplurality of substantially continuous synthetic filaments such ascellulose acetate, natural fibrous threads and synthetic filaments ormixtures of differ ing synthetic filaments encased in a plastic sheath.

8 Claims, 3 Drawing Figures 1 BALL POINT PEN BACK END CLOSUREConventional ballpoint pens include an ink or fluid reservoir from oneend of which'the typicalapplicator or writing tip protrudes. This tip,of course, is in contact with the ink and the opposite end of thereservoir is commonly open to the atmosphere so that air may enter thereservoir and displace the writingfluid as it is expelled from thewriting tip. Ordinarily, the meniscus of the ink column'or a followerprevents the ink from flowing back through the open end of thereservoir, however, if the pen is jarred violently or a break occurs inthe ink film at the ballpoint, the ink may leak from the open backend'of the reservoir. Leakage'of this type is quite undesirable since itmay soil not only the users work product, but also his wearing apparel.

In attempting to alleviate this leakage, air-permeable plugs or stoppersof porous materials, such as sintered metal, urethane foams'and treatedfelts or the like have been inserted in the reservoir back-end opening.These have usually been separated by an air space from the not attainedthe degree of reliability that is required for such manufacturingtechniques. In some instances, placement of stoppersin the reservoir ismade difficult due to the size and unusual construction of the stopper,and this mayresult in an improper insertion and fit, thus creating aleaker. Neither is it uncommon for conventional stoppers to impair theflow of air into the reservoir so that the ink will not flow properly tothe writing tip. In other situations of backflow past the stopper, thecause usually lies largely in the fact that the'pores of thestopper aretoolarge. On the other hand, in instances of insufficient ingress of airto produceprloper writing action, the pores of the stopper are toosmall, either in the stopper material itself as initially'formed, or asa result of itscompression during installation in the reservoir.

This invention, among other things, provides a backend pen plugconstruction that is readily adaptable to high volume productivitybecause of the insertion and cut-off technique which may be employed inthe manufacturing assembly process. As is more fully discussed below,this plug construction includes a plastic sheath within which there isretained a bundle of synthetic filamentous material. Similarly, it may,on occasion, be advantageous to use several different synthetic fibersor cotton and synthetic fibers in these plugs to lend additionalstrength to the bundle for processing purposes. Further, in eachinstance that fiber which is being relied upon for strength will beuncrimped and unbulked whereas the sealing synthetic fiber may becrimped and bulked or uncrimped and unbulked. I I

The compression of these fibers one upon the other a and fusion of theoutermost fibers with the sheath eliminate any potential direct path.between the plug ends through whichink might flow. Likewise,'thecompression fit between the exterior of the plug and the reservoir tendsto completely seal this area so that in the event of pen failure, noleakage will be experienced around the plug perimeter.

Accordingly this back-end plug provides a reliable stopper means thatmay be used inside a separate ink cartridge intended for use in a pen orin the reservoir of a pen that is either directly filled or employs acartridge.

With the foregoing more important features in mind and withsuch otherfeatures as may become apparent as this specification proceeds, theinvention will be understood from the following description taken inconjunction with the accompanying drawings, wherein like characters ofreference are used to designate like'parts and wherein: I I w FIG. 1 isan exploded partially cross-sectioned plan view of a typical ballpointpen incorporating the airperrneable plug of this invention;

FIG. 2 is an enlarged cross-section of an extended length ofair-permeable plug material prior to incorporation in a ballpoint pen orsimilar writing instrument;

FIG. 3 is a transverse cross-section taken along line 3-3 of FIG. 1. v

Referring now to the accompanying drawings in detail, and moreparticularly to FIG. 1, the reference numeral l0 designates a typicalballpoint pen. This pen, of course, further includes a barrel member 11interior of which is a fluid reservoir 14, a writing tip or applicator12, and-a stopper or back-end plug 16 which is airpermeable yet forms apositive obstruction to writingfluids. Thus, the stopper 16 will permitthe ingress of air to displace theoutgoing ink at the writing tip andyet will prevent theback flow of ink 18 out of'the reservoir 14.Similarly, as is common to such pens, there is provided a cap member 20to shield the tip 12 when the pen is not in use.

The stopper or back-end plug 16 is a sheathed bundle of fibers and ismore fully described hereinbelow. Such stopper, however, is positionedat the rear the fluid reservoir 14in a typical press type fit. It shouldalso be obviousfrom FIG, 1 that this form of stopper may be equallyeffectively used in the back-end portion of a ballpoint pen or similarwriting fluid cartridge. Similarly, two or more stoppers of this typemay be'employed in series and when several are so used, they may eitherabut or be spaced from one another. In any event, an air space 22 shouldbe retained between the stopper or stoppers and the writing fluid or ink18.

FIG. 2 illustrates in cross-section the intermediate tubular product 16Afrom which the air-permeable plugs 16 are severed during the penmanufacturing sequence.

Each of these plugs-is preferably comprised of an uncrimped, unbulkedbundle of filamentous material 24 low-twist, cellulose acetate materialhaving between about 3,000 and 25,000 total denier and beingsubstantially parallelely arranged in the sheath 26. Altematively, thecellulose acetate fibers may be crimped and bulked prior to theirencasement in the sheath 26.

Likewise, in certain instances, it may be desirable to incorporate othersynthetic fibers, for example, polyester materials into the bundle inorder to strengthen the filamentous mass for processing purposes.Preferably such added fibers would be uncrimped and would be positionedon the periphery of the bundle adjacent the sheath 26. Further, it isconsidered practical to use up to 40 percent of the total bundle ofpolyester material in these applications.

It is also conceived that an intennixture of natural (mercerized cotton)and synthetic fibers, for example, cellulose acetate, may also providean effective stopper. In this instance, the cotton will lend strength tothe bundle as it is being processed into plug form and may include asmany as 50 such threads.

In each instance, however, the sheath 26 will preferably have an insidediameter of between about 0.025 inch and 0.250 inch and be made of asuitable plastic such as polypropylene or the like. Plug material 16Atherefore may be manufactured by extruding the sheath over a suitablyarranged filamentous bundle typical of which is six strands of 240 endseach.

It should also be obvious from FIG. 3, in particular, that the press fitof back-end plug 16 in pen barrel 11 is such that it seals any possiblefluid passageway between the outer surface of sheath 26 and the boresurface forming the fluid reservoir. This then provides the user with amore reliable obstruction member in that positioning of the stopper inthe reservoir backend opening is not critical to produce a good seal.Similarly, the intermediate product 16A is one which lends itself toease of handling for the pen manufacturere. Thus, it should be obviousfrom the above that an improved stopper construction is here disclosedwhich in all respects represents a substantial advance of the prior artproducts and techniques.

In operation and so long as the ink remains out of contact with the plugair may find its way into the interior of the pen barrel and therebydisplace the ink 18. Upon pen failure, however, the ink may flow to therear of the barrel 11 and, of course, begin to permeate the plug. Thedense synthetic fiber bundle and particularly the cellulose acetate willattenuate this flow and thereby begin a plugging action within thebundle. Additionally, contact of the acetate with typical pen inksproduces a swelling action which further compresses the bundle andeffectively produces a positive blockage to further flow as well as theingress of air.

While in the foregoing there have been described and shown the preferredembodiments of the invention, various modifications may become apparentto those skilled in the art to which the invention relates. Accordingly,it is not desired to limit the invention to this disclosure and variousmodifications and equivalents may be resorted to, falling within thespirit and scope of the invention as claimed.

[claim:

1. An air-permeable plug adapted to act as a positive obstruction towriting fluids typically used in writing implements and comprising asubstantially continuous sheath having an inside diameter of betweenabout 0.025 and 0.250 inches and a low twist substantially continuousparallelly arranged filamentous material having a total denier ofbetween about 3,000 and 25,000 encased in said sheath and furthercharacterized by its perviousness to air and its imperviousness towriting fluids when exposed to and contacted therewith.

2. A plug according to claim 1 wherein said filamentous material isuncrimped and unbulked cellulose acetate.

3. A plug according to claim 2 wherein said filamentous material furtherincludes a plurality of substantially continuous parallelly arrangedpolyester fibers positioned around the periphery of said celluloseacetate and adjacent said sheath.

4. A plug according to claim 2 wherein said filamentous material furtherincludes a plurality of substantially continuous parallelely arrangedcotton threads intermixed with said cellulose acetate.

5. A plug according to claim 1 wherein said sheath between about 0.025and 0.250 inches in diameter and is of a polypropylene construction.

6. Awriting implement including in combination a fluid reservoircontaining an ink supply, an applicator in contact with said ink supplyand a back-end plug means comprised of a substantially parallellyarranged bundle of filamentous material having a total denier of betweenabout 3,000 and 25,000, said means being further adapted to permitpassage of atmospheric air while preventing backflow therethrough of thecontent of the reservoir.

7. A writing implement according to claim 3 wherein said plug means alsoincludes a substantially continuous sheath having an inside diameter ofbetween about 0.025 and 0.250 inches, said sheath encasing and retainingthe bundle of filaments and being tightly positioned in an opening tosaid reservoir.

8. A writing implement according to claim 7 wherein said sheath is of apolypropylene construction.

2. A plug according to claim 1 wherein said filamentous material isuncrimped and unbulked cellulose acetate.
 3. A plug according to claim 2wherein said filamentous material further includes a plurality ofsubstantially continuous parallelly arranged polyester fibers positionedaround the periphery of said cellulose acetate and adjacent said sheath.4. A plug according to claim 2 wherein said filamentous material furtheRincludes a plurality of substantially continuous parallelely arrangedcotton threads intermixed with said cellulose acetate.
 5. A plugaccording to claim 1 wherein said sheath between about 0.025 and 0.250inches in diameter and is of a polypropylene construction.
 6. A writingimplement including in combination a fluid reservoir containing an inksupply, an applicator in contact with said ink supply and a back-endplug means comprised of a substantially parallelly arranged bundle offilamentous material having a total denier of between about 3,000 and25,000, said means being further adapted to permit passage ofatmospheric air while preventing backflow therethrough of the content ofthe reservoir.
 7. A writing implement according to claim 3 wherein saidplug means also includes a substantially continuous sheath having aninside diameter of between about 0.025 and 0.250 inches, said sheathencasing and retaining the bundle of filaments and being tightlypositioned in an opening to said reservoir.
 8. A writing implementaccording to claim 7 wherein said sheath is of a polypropyleneconstruction.